<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #div1{
            width: 200px;
            height: 200px;
            background: skyblue;
            border-radius: 50%;
            position: absolute;
            right: 0;
            bottom: 0;
        }
    </style>
</head>
<body style="height: 2000px;">
  <div id="div1"></div>

  <script>
      var oDiv = document.getElementById('div1');
      var timer = null;
      window.onscroll = function () {
          var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
          startMove(document.documentElement.clientHeight-oDiv.offsetHeight+scrollTop);

      };

          function startMove(iTarget) {
             clearInterval(timer);
             timer = setInterval(function () {
                var speed = (iTarget-oDiv.offsetTop)/4;
                speed = speed>0?Math.ceil(speed):Math.floor(speed);

                if(oDiv.offsetTop == iTarget){
                    clearInterval(timer);
                }
                else{
                    oDiv.style.top = oDiv.offsetTop+speed+'px';
                }

             },30)
          }

  </script>
</body>
</html>